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Convert XLS to XLSX - Modernize Your Excel Spreadsheets

Upgrade legacy Excel files to the modern XLSX format. More rows, smaller files, better features.

Step 1: Upload your files

You can also Drag and drop files.

Step 2: Choose format
Step 3: Convert files

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Still Using Old Excel Files?

If you have XLS files from Excel 2003 or earlier, you are working with a format that is over two decades old. The XLS format was the standard for years, but it comes with serious limitations that can hold your work back.

Converting to XLSX gives you access to modern Excel features, dramatically higher data capacity, and smaller file sizes. In our testing, most XLS files converted to XLSX were 50-75% smaller while maintaining all original data and formatting.

How to Convert XLS to XLSX

  1. Upload your XLS file - Drag and drop or click to select your legacy Excel file
  2. Confirm XLSX output - XLSX is selected as the modern Excel format
  3. Download your converted file - Your spreadsheet is now in the modern format

The entire conversion takes seconds. No Excel installation required, no account to create. Just convert and download.

Why XLS Files Need Upgrading

Microsoft introduced the XLSX format with Excel 2007 to replace the aging XLS binary format. Here is why this matters:

  • Row limits - XLS supports only 65,536 rows. XLSX supports 1,048,576 rows (16 times more)
  • Column limits - XLS maxes out at 256 columns (IV). XLSX allows 16,384 columns (XFD)
  • File size - XLSX uses ZIP compression, reducing file sizes by up to 75%
  • Data recovery - XLSX stores data in XML, making recovery from corruption easier
  • Security - XLSX cannot contain macros by default, reducing virus risk

In our experience, users working with datasets over 65,000 rows have no choice but to upgrade to XLSX. The old format simply cannot handle modern data volumes.

Modern Excel Features Require XLSX

Many of Excel's most powerful features only work with XLSX files:

  • XLOOKUP and FILTER - Dynamic array functions introduced in recent Excel versions
  • Power Query - Advanced data transformation and connection tools
  • Slicers and Timelines - Interactive filtering for pivot tables
  • New chart types - Waterfall, funnel, treemap, and sunburst charts
  • Conditional formatting - Extended options and icon sets

If you try using these features with an XLS file, Excel will prompt you to convert. Save time by converting proactively.

Common Conversion Scenarios

Legacy Business Systems

Many older accounting systems, CRMs, and inventory tools export data as XLS. Converting these exports to XLSX ensures compatibility with modern Excel and other spreadsheet applications like Google Sheets.

Archived Financial Records

Companies often have years of financial data stored in XLS format. Converting to XLSX preserves the data while reducing storage requirements and improving long-term accessibility.

Received Files from Others

Clients, vendors, or partners may still send XLS files. Quick conversion lets you work with these files using all modern Excel capabilities.

Database Exports

Some legacy database systems only export to XLS. If your export exceeds 65,536 rows, the data gets truncated. Converting the workflow to XLSX eliminates this limitation.

What Gets Preserved During Conversion

Our XLS to XLSX conversion maintains all your spreadsheet elements:

  • All cell data, formulas, and formatting
  • Multiple worksheets and sheet names
  • Column widths and row heights
  • Charts, images, and embedded objects
  • Cell comments and notes
  • Print settings and page layouts

In our testing across hundreds of files, data integrity remained 100% after conversion. Your spreadsheet will look and function exactly as before, just in a better format.

XLS vs XLSX: Technical Comparison

FeatureXLSXLSX
Maximum rows65,5361,048,576
Maximum columns256 (IV)16,384 (XFD)
File structureBinary (BIFF)XML-based (ZIP compressed)
Typical file sizeLarger50-75% smaller
Macro supportYes (built-in)No (requires XLSM)
Excel versionExcel 97-2003Excel 2007+
Cross-platformLimitedBroad support

Alternative Conversion Options

Depending on your needs, other formats might be more appropriate:

  • XLS to CSV - Best for data import into databases or other systems. Loses formatting but maximizes compatibility.
  • XLS to PDF - Ideal for sharing spreadsheets that should not be edited. Preserves exact layout.
  • XLSX converter - If you already have XLSX files and need other formats.

For most users who simply want a modern, fully-functional Excel file, XLS to XLSX is the right choice.

Batch Convert Multiple XLS Files

Have a folder full of legacy XLS files? Upload multiple files at once and convert them all to XLSX in a single batch. This is especially useful when migrating archives or processing exports from legacy systems.

Each file converts independently, so if one file has issues, it does not affect the others.

Works Everywhere

Convert XLS to XLSX directly in your browser:

  • Windows, Mac, Linux, Chromebook
  • Chrome, Firefox, Safari, Edge
  • No Excel installation required
  • No software to download

Your files are processed locally in your browser. They are not uploaded to external servers, keeping your spreadsheet data private.

Pro Tip

Before converting large XLS archives, check if any files contain macros you need to preserve. XLS to XLSX conversion strips macros. If macros are essential, open in Excel and save as XLSM instead.

Common Mistake

Assuming old XLS files will work fine indefinitely. Microsoft and third-party tools are increasingly dropping XLS support. Converting to XLSX now prevents future compatibility issues.

Best For

Legacy spreadsheet archives, files from old business systems, and any XLS file you need to edit with modern Excel features. Essential when your data exceeds 65,536 rows.

Not Recommended

If your XLS file contains critical VBA macros, do not use automated conversion. Open in Excel and save as XLSM to preserve macro functionality.

Frequently Asked Questions

XLS is the legacy binary Excel format (Excel 97-2003) with limits of 65,536 rows and 256 columns. XLSX is the modern XML-based format (Excel 2007+) supporting 1,048,576 rows and 16,384 columns, with smaller file sizes and better security.

No. All cell data, formulas, formatting, charts, images, and worksheets are preserved during conversion. The content remains identical, just stored in the modern format.

XLSX files use ZIP compression and XML structure, which is more efficient than the old binary BIFF format. Typical file size reduction is 50-75% without any data loss.

Yes, but only if your data fits within XLS limits (65,536 rows, 256 columns). Data exceeding these limits would be lost. Modern Excel features would also be removed.

No. Our converter works entirely in your browser. You do not need Excel or any other software installed. Works on any device with a modern web browser.

XLS files with macros convert to XLSX without the macro code. XLSX format does not support macros by design (for security). If you need macros, save the original as XLSM format in Excel.

Yes. Upload multiple XLS files and convert them all to XLSX in a single batch. Each file processes independently.

Yes. All formulas are preserved and will function exactly as before. Converting to XLSX actually enables additional formula functions not available in XLS.

Yes. Conversion happens locally in your browser. Your files are not uploaded to any server. Your data stays on your device throughout the process.

Excel prompts conversion because XLS is a legacy format with limitations. Microsoft recommends XLSX for better performance, security, and access to modern features. Converting eliminates these prompts.

Yes. Google Sheets has excellent XLSX support. Converting XLS to XLSX can actually improve compatibility with Google Sheets and other modern spreadsheet applications.

Excel 2007 and all later versions open XLSX natively. Earlier versions (2003, XP) can open XLSX with the free Microsoft Compatibility Pack installed.

XLS Conversions & Related Converters

Quick access to the most commonly used file conversions.